Angular dependence of the exchange bias and the jump phenomenon

Abstract

Based on the principle of minimal energy, the angular dependence of exchange bias for ferromagnetic/ antiferromagnetic bilayers has been investigated in detail. The competition between unidirectional and uniaxial anisotropies divides the initial magnetization state of the bilayer into monostable and bistable states, which determine the angular dependence of exchange bias directly. When the bilayer is in the bistable state, the exchange bias field and the coercivity will display a jump phenomenon at the orientation angles of the intrinsic hard axes. The jump phenomenon in the angular dependence of exchange bias has been explained by analyzing the magnetization reversal processes. The numerical calculations show that both the exchange bias Held and the coercivity are larger in the magnitude at the points of the jumps. This jump phenomenon is an intrinsic property of the bilayers which is dependent on exchange coupling constant, the thickness and the uniaxial anisotropy constant of the ferromagnetic layer.